Three years ago, astronomers discovered ancient mysterious objects known as “little red dots.” They exhibit characteristics of both galaxies and supermassive black holes, but they don’t exactly match the description of either.
Now, a new study has found that these strange dots may be young supermassive black holes after all.
Astronomers first observed the little red dots through the James Webb Space Telescope (JWST) at the end of 2022. They only existed for a short time, in terms of the universe. They first appeared less than a billion years after the Big Bang and almost disappeared completely after two billion years.
There were two theories as to what the unusual objects could be. One possible explanation was that they were star-rich galaxies. The other possibility was that they might be early supermassive black holes.
Light coming from energized hydrogen atoms around the red dots suggests that the gas is moving rapidly at thousands of miles per second, rushing toward the strong gravitational pull of the black holes.
However, both supermassive black holes and star-rich galaxies were both too large of objects to have formed so early in the history of the universe.
Additionally, supermassive black holes are supposed to emit X-rays and radio waves, but scientists haven’t detected any coming from the little red dots.
For the new study, the researchers examined spectra from 30 little red dots. The light shining from the little red dots was very similar to the light that would be emitted from a supermassive black hole shrouded in a thick cloud of gas. The gas cloud could’ve blocked X-ray and radio waves from reaching JWST.
The research team then analyzed the light from the little red dots to determine the speed at which the gas was moving, which was about 670,000 miles per hour.
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When they recalculated the masses of the little red dots, the team found that they were about 100 times less massive than previously believed. Overall, the findings imply that the little red dots are supermassive black holes surrounded by gas.
“These objects turned out to be supermassive black holes despite missing almost all typical indications of massive black holes,” said Vadim Rusakov, the lead author of the study from the University of Manchester in England.
“They have an almost perfect disguise that removes X-ray and radio emission.”
In the future, scientists may learn more about how these supermassive black holes were born in the first place. They will need to study more little red dots in depth to determine how common it is for the dots to be surrounded by a gas cloud and how the gas contributes to the growth of black holes.
“If we are lucky, little red dots may still preserve clues from the time when they were formed—whether it’s the gas chemistry or some useful physical property of the black holes and their cocoons that can help to differentiate between different theories,” said Rusakov.
“This is one of the biggest remaining questions in astrophysics, and it seems that we are closer than ever to being able to answer it.”
The study was published in the journal Nature.
By Emily Chan
Emily Chan is a writer who covers lifestyle and news content. She graduated from Michigan State University with a degree in... More about Emily Chan
